The Validation & Pathology Core consists of personnel with expertise in clinical gastroenterology, advanced procedures (endoscopic mucosal resection, endoscopic ultrasound), specimen processing, molecular biology, and pathology. Core personnel have many years experience in validation methods. The specific role of this BETRNet Specialized Research Rescource (Core) is to support the Research Center in the design and analysis of validation studies for the binding activity of fluorescent-labeled peptides to high-grade dysplasia and early adenocarcinoma for imaging in Barrett's esophagus. This Core will also support the three Primary Research Projects, developmental (Pilot) projects, cross-BETRNet projects, and other cross-BETRNet activities by providing methods and services for pathological evaluation of tissue specimens, including EMR and biopsy. The Validation & Pathology Core is organized into two parts: 1) the validation group which consists of clinical investigators and support staff that will recruit human subjects, collect specimens of Barrett's esophagus, administer selected fluorescent-labeled peptides, collect fluorescence images, and register fluorescence intensities with histopathology. These studies will be performed to validate affinity binding of the panel of peptides selected against amplified and overexpressed genes identified on the genomic database. Validation is critical to selection of an optimized set of peptides to be validated in the Phase 1 clinical studies with the proposed novel targeted imaging strategy; and 2) the pathology group which consists of gastrointestinal pathologists who will provide rigorous histopathology evaluation of the esophageal specimens that will be registered with the fluorescence images to sub-millimeter resolution.